Now, this is the first time using the up/own rudder lines - which seems to work great and I have had no problems. However, once the boat gets up to a fast speed - about 7 mph there is a definite humming and vibration coming from the rudder I believe. I have handle bungied all the way down. No humming at slower speeds.

I can feel it in the tiller handle and the hull and pretty sure it is in the stern rudder area. The sound it makes is like tie down strap vibrating in the wind while driving.Never had that on either 2007 boats with older up/down single handle.

The sound is not entirely unpleasant, in fact it adds a sensation of speed. The Island is literally "humming" along

Q. Has anybody else experienced this phenomenon?

Is this a result of the bungie cord down line acting like a guitar string when attached to the rudder?

I assume this vibration is also not a problem of something that needs adjusting?

Hull speed on a 16 foot boat is just over 5 knots or about 6mph. So you are pushing over your bow wave and starting onto a plane around that speed.If you have access to a planing speedboat, try going from no wake speed up to planing as SLOWLY as you can. Speedboats will also shudder, but you usually just jump on the throttle and accelerate through it so fast that you don't really notice. As you go over the hull speed (1.34 times the square root of the waterline in feet gives hull speed in knots) you will notice the stern will squat down as it sinks into the trough of the bow wave. Somewhere in there it will finally crest the bow wave and zip off merrily, free from the bow wave restriction.Sort of like breaking the sound barrier. Most sailing hulls that can plane will start to shudder, and set up some interesting harmonic vibrations on their way onto a plane.Note also that your GPS is giving you speed made good, and not actual speed through the water. You could convert if you are tracking your speed and direction with the GPS against the speed of any water currents, but that will involve some trigonometry. At any rate, it would only indicate that everything is working extremely well, including the operator - it's not easy to get a sailboat up a plane!

I noticed that mine got a definite vibration through the rudder when I sailed at a reasonable speed with the Turbo ST drive fins in the up position. This disappeared when I moved them away from the hull. It didn't do it with the original fins fitted. Wonder if you are experiencing the same thing?I intend to sail with the fins approx 1/2 way down.

I noticed that mine got a definite vibration through the rudder when I sailed at a reasonable speed with the Turbo ST drive fins in the up position. This disappeared when I moved them away from the hull. It didn't do it with the original fins fitted. Wonder if you are experiencing the same thing?I intend to sail with the fins approx 1/2 way down.

I've experienced the same Yakaholic and rokraider. I thought it was coming more from the drive than the rudder though. I'll have to pay more attention next time it occurs.At speed the turbo's do flutter/vibrate as well when up against the hull. That's why I prefer to remove the drive if conditions are right. At about 45 degrees the drive is quieter when under sail only.

Steve0 wrote:

Note also that your GPS is giving you speed made good, and not actual speed through the water. You could convert if you are tracking your speed and direction with the GPS against the speed of any water currents, but that will involve some trigonometry.

SteveO,I find the Hobie pitot tube helps with estimating current. Normally the ball is showing about half my GPS km/h speed. If its not the the difference is due to the current (or some weed is blocking the intake! )